Apparatus for the determination of plating characteristics of plating baths



Aug. 6,- 1957 o. HULL ET AL 2,801,963

R. APPARATUS FOR THE DETERMINATION OF PLATING CHARACTERISTICS OF PLATINGBATHS Filed Dec. 8, 1953 2 Sheets-Sheet l INVENTOR. ,/chwea 0, Hull.JOHN B. h/IIVTEPJ Aug. 6, 1957 R. o. HULL ET AL 2,801,963

APPARATUS FOR THE DETERMINATION OF PLATING CHARACTERISTICS OF PLATINGBATHS 2 Sheets-Sheet 2 Filed DeC. s, 1955 INVENTOR.

l/cx/aeo O. HUAA BY Jam/u a [MA/r525 2,801,963 Patented Aug. 6, 1957United States atent fiice APPARATUS FOR THE DETERMINATION OF PLATING'CHARACTERISTICS OF PLATING BATHS RichardYO. Hull, RockyrRiver, and JohnB. Winters, Westlake, Ohio, assignors to Ann F. Hull and Adrian Medert,as cotrustees, Cleveland, Ohio Application December 8', 1953, Serial No.396,815 7 Claims. (Cl. 204-495) This invention relates to theelectrodeposition of metals and. more particularly to apparatus for theexamination, e luation, and determination of the platingcharacteristi'cs of a plating bath or a series of plating baths used ina sequence of'plating operations.

Heretofore, it has been the practice in the electrodeposition of metalsto examine or evaluate the plating characteristics-eta plating bathbytaking samples thereof and-"subjecting them to examination underlaboratory conditions. This practice and the apparatus employed isclearly. set forth in United States Patent No. 2,149,344 to R. O.Hulhdated March 7, 1939. It has also been the priorpractice to attemptto determine, in a limited way the behavior of a single plating bathunder operating conditions simply by immersing a flat plate or bentcathode in..the platingbath, suspended from the cathode busbar. Ithasalso been the practice in determining the various current densitiesobtained in a plating bath, or irregularly shaped articles, to use aprobe electrode to measure the current passing to various parts of suchan article from the cathode busbar.

Theprior practices referred to above left a great deal to-be desired inevaluating and determining the plating characteristics of a plating bathor a series of plating operations includingfor example, cleaning,pickling, and

I rinsing, followed by copper, nickel or chromium plating.

Any fault or defect in any one of such a sequence of operations,numbering in some cases as many as ten to twelve consecutive steps, willresult in a defectively plated product. Moreover, it was extremelydiflicult to ferret out the particular fault in the sequence ofoperations with the limited means available for testing, and it has beennecessary to attempt. to trace the source of each fault by trial anderror with the result that an excessive amount of'rejected platedproducts was experienced. Furthermore, it has been. difficult orimpossible to establish the optimum. operating conditions, such ascurrent density, temperature and bath compositions, in a plating bath orsequence of plating operations by simple test methods carried on-remotetherefrom by reason of the failure to simulate or duplicate operatingconditions under such test methods. Hence it has been difficult tocontrol the plating operations to obtain optimum results at all times.This-has been particularly true with respect to alloy plating..such as.brass plating in which variations in current density either are singlepoint or throughout the bath produce undesirable variations incomposition of deposit. Accordingly, there has been no simple means fordetecting a fault in. a. plating sequence under actual plating operatingconditions so that the difficulty or difficulties resulting inunsatisfactorily plated products can be pinpointed easily andaccurately.

The foregoing discussion of the prior practices is true not only ofstill plating, wherein the objects to be plated are immersed in a singletank of plating solution until: the. desiredthickness of deposit isobtained, but it is even more applicable to automatic or continuousplating machines wherein objects or racks of objects to be plated aremechanically transported from one tank to another and through each tank,so that a series of operations, such as cleaning, rinsing, pickling,plating, dipping, etc., can be carried out in sequence without handlingthe objects or racks between operations. Such automatic plating machinesare extensively used in the electroplating industry, and for successfuloperation it is essential to know what the actual working conditionsareat all times in all parts of the system, so that changes andadjustments in operating conditions within the various units may be madewith respect to each other, to obtain uniform andsatisfactory platingresults.

The foregoing drawbacks prevalent in prior methods oftesting platingbaths have been completely surmounted by the present invention.

Our invention is designed to assure obtaining satisfactory results byproviding a simple means to determine the plating characteristics of asingle bath, or of a series of baths in a plating sequence, whether in amanually operated system or in a fully automatic mechanically operatedplating machine. Our apparatus can be put through one or all or anynumber of the steps in a plating sequence to determine a singlecharacteristic or the cumulative results produced by the system. Notonly does our invention determine the plating characteristics of thebaths, but also provides a means for determining the nature of thedeposit, either in one bath or cumulatively through a sequence ofoperations. Our apparatus provides-a simple means for determining andcontrolling such factors as brightness of deposit, uniformity ofcomposition of an alloy deposit, uniformity of current distribution,optimum current density range for producing a desired result, and anyother factor that is essential in establishing, and maintaining optimumoperating conditions in a plating bath or a sequence of platingoperations.

t is among the objects of the present invention to provide apparatus fordetermining the plating characteristics of a plating bath under actualproduction conditions.

Another object of the invention is to provide apparatus to determine thecharacteristics of the electrodeposit upon an article at any point in asequence of plating operations.

A further object of the invention is to provide apparatus for producinga test plate under actual operating conditions covering the entire rangeof current densities of theplating bath whereby the optimum currentdensities to be used may be determined.

A still further object of the invention is to provide apparatus adaptedto be suspended from the cathode busbar of the plating bath and movedthrough the plating bath, to indicate the current densities existingwithin the plating bath at every point of its path of traveltherethrough.

A still further object of the invention is to. provide apparatus todetermine in the plating bath, the proper distribution andplacing ofanode material with relationto the article being plated.

Another object of the invention is to provide apparatus for producing atest plate which would reflect deviations from the optimum operatingcondition of any plating bath relative to any other plating bath in asequence of plating operations to produce an optimum plate.

Another object of the invention is to provide apparatus for determiningthe source and cause of undesirable results in a sequence of platingoperations such as are encountered in an automatic continuous plating:machine These and other objects and advantageous features of theinventionnot at this time more particularly pointed out will becomeapparent as the nature of the invention isbetter understood. from thefollowing detailedzdescription taken in conjunction with theaccompanying drawings, wherein like reference characters denotecorresponding parts, and wherein:

Figure l is a side elevational view partly broken away of a device fordetermining the plating characteristics of a plating bath embodying thepresent invention,

Figure 2 is a front elevational view with parts in section of the deviceillustrated in Figure 1,

Figure 3 is a view taken on the line 3-3 of Figure 1,

Figure 4 is a top plan view taken on the line 4-4 of Figure 1,

Figure 5 is a fragmentary detail view taken on the line 55 of Figure 4,

Figure 6 is a sectional view taken on the line 6-6 of Figure 5,

Figure 7 is a fragmentary detail View taken on the line 7-7 of Figure 6.

Figures 8 and 9 are transverse and longitudinal sectional views,respectively, of a plating tank illustrating the use of the presentinvention therein.

With reference to the accompanying drawings there is illustrated adevice for determining the plating characteristics of a plating bath,constructed in accordance with the present invention and comprising ahollow container generally indicated by the number llll having arectangular vertically disposed opening. In the embodiment illustratedthe container takes the shape of a hollow trigonal prismatic figurehaving side walls 12 and 13 angularly disposed with respect to eachother, a top wall 14 and a bottom wall 15. The walls of the containerare joined together in any suitable manner being formed of anon-conducting material which is impervious to the action of a platingbath, such as a transparent synthetic resin, namely polymerized methylmethacrylate sold in the trade under the name Lucite. The top and bottomwalls 14 and 15 are longitudinally slotted as at 16 and 17,respectively, adjacent the side wall 13 to receive a test plate or panel18 arranged in a vertical position within the container, parallel to theside wall 13. Adjacent the intersection of the side walls 12 and 13 thelatter is provided with an aperture 19. Secured to the outer surface ofthe wall 13 is a member 20 having an opening therethrough in alignmentwith the aperture 19. A plug 21 having a contact 22 on the outer endthereof is received in the aperture 19, the contact being arranged toengage the test plate 18 and convey current thereto as will be disclosedhereinafter. The plug 21 is maintained within the aperture 1% by meansof a flexible strip member 23 having a bifurcated end 24 which slidablyengages l the neck portion of plug 21. The other end of the strip isslidably mounted within a slotted block 25 secured to the outer surfaceof the side wall 13.

Suitable openings 13A are provided in the top and bottom walls 14 and15, respectively, adjacent the apex between the side walls of thecontainer to provide escape of air upon insertion of the container intothe plating bath and drainage of solution from the container uponremoval from the bath.

The container 10 carrying the test plate 155 is adapted to be suspendedfrom the cathode busbar of a plating tank A diagrammatically illustratedin Figures 8 and 9 of the drawings. The tank A contains the usual anodebusbars 27 from which the anode material 28 to be plated is suspended inthe plating bath 29. The cathode busbar is indicated by the numeral 3 itis to be understood that the term busbar is used in the specificationsand claims to indicate the means of connecting the apparatus in theelectrical circuit.

The supporting assembly for the container 10 includes a hanger member 31having a substantially horizontal portion 32 with hook members 33 formedon the ends thereof. The hanger 31 is made of any suitable currentconducting material and the hooks 33 are arranged to hang over thecathode busbar. The horizontal portion 32 of the hanger seats within ahorizontal slot 35' formed in the rear face of the housing 36 of anammeter 37 provided with a dial 38 from which readings may be obtainedof the current passing therethrough. The hanger is secured to thehousing 36 by means of spaced bolts 39 the inner end of one bolt beingconnected to one terminal of the ammeter 37 by conductor 40.

A bracket member 42 is arranged to connect the ammeter 32 to the upperend of a column 43 leading to the container it}. The bracket member isin the form of a bar having one end 44 turned at an angle thereto andsecured to the housing 36 by means of a bolt 45, the inner end of whichis connected to the other terminal of the ammeter by means of conduit46.

The column 43 comprises a cubical block 47 suitably nod to the uppersurface of the top wall 14 of the container iii and is bored as at 48and counter-bored as at 49 to receive the lower end of a tubular member50. The upper end of the tube 50 receives the shank portion 51 of acylindrical member 52. The upper surface of the member 52 is providedwith intersecting transverse slots 53 which receive the free end of thebracket 42. A conductor tube 54 is mounted within the tube 50 having oneend engaging within the shank 51 and the other end seating within thebore 48 of the block 47. A threaded bolt extends from the upper end ofthe bar 54 and is secured to the bracket engaging within one of theslots 53 of collar 52. The column 43 is constructed of sufficientrigidity and weight to assume a vertical position in the plating tankand maintain the container in a predetermined fixed position in thebath. To this end the conductor tube 54 is filled with weighted materialand the cylindrical block 54A is provided in the lower end of the tube50.

Theblock 47 is provided with a horizontal bore 56 which traverses thebore 48 and is adapted to receive a conductor member 57 which isthreaded through the lower end of the bar 54. The outer end of the bore56 is provided with a terminal outlet 5% which receives a plug 60. Aninsulated conductor connects the plugs 60 and 19. in using the device ofthe present invention current flows from the cathode bar 3%, thru hanger31 to one of the bolts 39, conductor 4t? to one terminal of the ammeter37, thru ammeter 37 to the other terminal thereof, thence throughconductor 46, bolt 35, bracket 42, bar 54, member 57, conductor 61 toterminal contact 22 engaging the test panel 18.

This invention provides a simple means for testing a plating bath bysuspending a flat test panel in the plating bath under operatingconditions which, by geometric configuration in a suitable container orholder, portrays the plating characteristics of the bath over the entirerange of current densities encountered in the bath. The optimum range ofcurrent densities is immediately determined by a close mathematicalrelationship between the location of the bright or operable range on thetest panel and the current read on the ammeter of the device. Anyclouds, blisters, uncovered areas or burnt deposits are immediatelyapparent by visual inspection of the panel. The invention when used in aplating sequence serves to record differences between operatingconditions of successive plating baths as is reflected on the testpanel. Where such diiferences result in an unsatisfactory productadjustments may be made in current density, temperature or bathcompositions so that the operating conditions in successive baths arecoordinated to produce the desired plate on the article under treatment.

Having thus described our invention what we desire to obtain by LettersFatent is defined in the appended claims.

We cl 1. Apparatus for determining the plating characteristics of aplating bath disposed in a plating tank having anode material immersedtherein and a cathode busbar comprising a supporting member suspendedfrom the cathode busbar, a hollow trigonal prismatic container havingone open side attached to the lower end of the supporting member, a testplate mounted vertically within the container angularly disposed withrespect to the open side of the container, and means for conductingcurrent between said busbar and the said test plate and means formeasuring the current flowing to said test plate.

2. Apparatus for determining the plating characteristics of a platingbath disposed in a plating tank having anode material immersed thereinand a cathode busbar comprising a hollow trigonal prismatic containerhaving one open side of rectangular shape, a test plate verticallymounted within the container, means for supporting said container withinsaid plating bath, means for conducting current between said cathodebusbar and the said test plate and means for measuring the currentflowing to said test plate.

3. Apparatus to be employed as a Hull cell in determining the platingcharacteristics of a plating bath disposed in a plating tank havinganode material immersed therein and a cathode busbar comprising a hollowtrigonal prismatic container having one open side to permit the flow ofthe plating bath into the container, a test plate vertically mountedwithin the container, means for supporting said container within saidplating bath during the operation of the plating tank, means forconducting current between said cathode busbar and the said test plate,and means for measuring the current flowing to said test plate.

4. Apparatus for determining the plating characteristics of a platingbath disposed in a plating tank having anode material immersed thereinand a cathode busbar comprising a hollow trigonal prismatic containerhaving one open side of rectangular shape, a test plate verticallymounted within the container and angularly disposed with respect to saidopening, means for supporting said container from said cathode busbarWithin the plating bath, and a conductor disposed within said supportingmeans for transmitting current between said busbar and the said testplate and means for measuring the current passing through the testplate.

5. Apparatus for determining the plating characteristics of a platingbath disposed in a plating tank having anode material immersed thereinand a cathode busbar comprising a supporting member suspended from thecathode busbar, a hollow trigonal prismatic container formed ofnon-conducting material having a rectangular open side to permit theintroduction of plating solutions into the container, a test platemounted vertically within the container closely adjacent one side wall,means for conducting current between said busbar and the said test plateand means for measuring the current flow to said test plate.

6. Apparatus for determining the plating characteristics of a platingbath disposed in a plating tank having anode material immersed thereinand a cathode busbar comprising a hollow trigonal prismatic containerformed of non-conducting material having a rectangular open side topermit the flow of electrolyte through the container, a hollowsupporting member adapted to suspend the container from the cathodebusbar within the plating bath, a test plate vertically mounted withinthe container and angularly disposed with respect to said rectangularopen side, conductor means contained within said supporting member forconducting current between said busbar and the said test plate, andmeans for measuring the current passing through the test plate.

7. Apparatus to be employed as a Hull cell in determining underoperating conditions the plating characteristics of a plating bathdisposed in a plating tank including anode and cathode busbars, anodlematerials suspended from said anode busbar, a hollow container made ofnon-conducting material suspended from said cathode busbar having arectangular opening therein, a test plate vertically mounted in thecontainer at an angle with respect to said opening, and means forconveying current between said cathode busbar and said test plate, saidtest plate adapted to receive a deposit of anode material from one endof the plate to the other which is indicative of the actual platingrange present in the bath.

References Cited in the file of this patent UNITED STATES PATENTS1,519,572 Wolf Dec. 16, 1924 2,149,344 Hull Mar. 7, 1939 2,500,206Schaffer et a1 Mar. 14, 1950 FOREIGN PATENTS 292,417 Great Britain June21, 1928

1. APPARATUS FOR DETERMINING THE PLATING CHARACTERISTICS OF A PLATINGBATH DISPOSED IN A PLATING TANK HAVING ANODE MATERIAL IMMERSED THEREINAND A CATHODE BUSBAR COMPRISING A SUPPORTING MEMBER SUSPENDED FROM THECATHODE BUSBAR, A HALLOW TRIGONAL PRISMATIC CONTAINER HAVING ONE OPENSIDE ATTACHED TO THE LOWER END OF THE SUPPORTING MEMBERS, A TEST PLATEMOUNTED VERTICALLY WITHIN THE CONTAINER ANGULARLY DISPOSED WITH RESPECTTO THE OPEN SIDE OF THE CONTAINER, AND MEANS FOR CONDUCTING CURRENTBETWEEN SAID BUSBAR AND THE SAID TEST PLATE AND MEANS FOR MEASURING THECURRENT FLOWING TO SAID TEST PLATE.